1. Field of the Invention
The invention relates to a disposable cassette intended for a metering pump for infusion and to the method of manufacturing it.
Low-cost single-use gravity-fed infusion lines are known. These are commonly used in hospitals for irrigation (with saline) or for injecting various sensitive drugs. The flow rate is estimated by counting drops in a drip chamber and is regulated by a slide clamp. Neither the stability nor the precision are sufficient for certain applications. What is more, the absence of any electronics means that the suitability of the drug treatment - quantity - timing - patient cannot be monitored and checked. However, gravity-fed infusion has the advantage of being very cost-effective.
Electronic diaphragm or peristaltic pumps and gravity-fed flow controllers are also known. This equipment and its single use are expensive.
Also available on the market are disposable cassettes for infusion. Such cassettes are described in particular in the international application published under the number WO 02/087664. The appended FIGS. 1, 2a, 2b and 3 correspond respectively to FIGS. 2, 7a, 7b and 12 of this international application. These disposable cassettes comprise at least three components, namely:                a hollow first component (a) forming a pump body, having an inlet (b) for the connection of an inlet tube and an outlet (c) for the connection of an outlet tube;        a second component (d) collaborating with the hollow first component (a) to form a pumping zone (e) and comprising a flexible part (f) having a diaphragm-forming zone (g) carrying an inlet valve (h), an inlet lug (l), an outlet lug (m) bearing an outlet valve (i) and a peripheral rib (k) extending around the periphery of the diaphragm-forming zone (g) and around the periphery of the inlet (l) and outlet (m) lugs; and        a rigid third component (j) which is distinct from the second component (d) and fits onto the hollow first component (a) with a view, in particular, to keeping the second component (d) in the hollow first component (a).        
These cassettes have, in particular, the following disadvantages:                when they are being used, the precision of the flow rate is insufficient, especially if the volume in each cycle is very small (of the order of 10 microlitres) because the diaphragm cannot be attached to the pump body repeatably enough across all of the manufactured batches;        sealing is not reliable because it is achieved by trapping the peripheral rib (k) of the second component (d) between the hollow first component (a) and the third component (j), as can be seen in the attached FIGS. 2a and 2b,         assembling the components that make up these cassettes presents problems of repeatability and therefore of retention of the diaphragm; and        these components have complex shapes and are therefore more difficult and more expensive to manufacture.        
It is an object of the invention to propose a disposable cassette for medical use which is simple, reliable, made up of a minimum number of component parts which are themselves easy to manufacture and to assemble. Because this cassette is disposable, its cost of manufacture has to be low and it needs to leave the smallest possible ecological footprint.